1. Field of the Invention
This invention relates generally to a mechanical interlocking device for use with multiple circuit breakers for preventing operation of more than one circuit breaker at a time.
2. Background Information and Description of the Prior Art
Circuit breakers provide protection for elect systems from electrical fault conditions such as current overloads and short circuits. Vacuum circuit breakers in particular are useful for controlling and protecting electrical systems. Vacuum circuit breakers typically include separable main contacts which are disposed within an insulating housing. Generally, one of the contacts is fixed relative to the housing and to an external electrical conductor which is interconnected with the circuit to be controlled by the circuit breaker. The other separable main contact is movable. In the case of a vacuum circuit breaker the movable contact assembly usually comprises a stem of circular cross-section having the contact at one end thereof enclosed in a vacuum chamber and a driving mechanism at the other end external to the vacuum chamber.
In many instances, several circuit breakers are used to control an electrical system. Often more than one circuit breaker is provided in order that one breaker will be operating while another is being serviced or replaced. In addition, multiple breakers provide redundancy to the system.
Circuit breakers of a high voltage type typically require a structure or a cell of sheet metal which houses and encloses the units for safety purposes and facilitates connection with the bus ducts and other auxiliary equipment. Typically, several circuit breakers are placed within a single cell housing.
As noted above, it is often desirable that only one circuit breaker be operable at any one time. In such a case, the other redundant circuit breaker must be separated from the electrical circuit so that it does not continue to operate in a situation where the primary circuit breaker has tripped. Previously, dual circuit breakers or multiple circuit breakers used as backups to a primary breaker had to be manually disengaged from the system to assure that they did not continue to operate. Although some mechanical locking devices may have been disclosed in the past for other types of circuit breakers, it has not heretofore been known to provide a mechanically operable system for the vacuum circuit breaker. It is important that a mechanical means of preventing two breakers from closing at the same time be provided in order to avoid use of electrical components which may malfunction in an electrical fault situation. In addition, it is preferable to provide an interlock system which can be utilized with both side to side, top to bottom, and diagonal installations of dual circuit breakers.
There remains a need, therefore, for a mechanical interlock device which is capable of preventing one circuit breaker in a set of breakers from operation while the other circuit breaker is operating. There remains a further need for a device which can be easily mounted in existing cell housings in a variety of configurations and which is a low cost and easy to install device. There is also a need for a device which allows one circuit breaker in a set of two circuit breakers to be removed for maintenance or service and reinstalled while the other circuit breaker is operating.